EXERCISE FOR WEIGHT CONTROL: WHY?

Guy Leahy

The cardinal principle of successful weight maintenance is if calories in=calories out = weight will not change. In order to lose weight and keep it off, one must devise a way to construct a calorie deficit, where the total number of calories consumed is less than the number of calories used, thereby requiring the body to make up this calorie difference by taking fat out of storage and using it for energy. Exercise can create such a calorie deficit in two ways.

1. Aerobic Exercise significantly increases the total number of calories burned per day due to activity. If, for example, one needs 2,000 calories a day to maintain a desired body weight, and uses 2,000 calories/day, one's body weight stays the same. However, if one exercises aerobically 5 X week, and burns off 500 calories at each exercise session, this has increased energy expenditure by 2,500 additional calories/week . this deficit has to be made up by burning stored body fat. This would mean the loss of an additional 2.9 pounds of body fat/month, just from exercise!
Aerobic exercise also increases the body's ability to burn fat as a fuel, and to do so at higher exercise intensities than would otherwise be the case. To be effective, though, the exercise must be for a minimum of 30 minutes/day, five days a week. However, the 30 minutes of exercise can be broken up into smaller sessions spaced throughout the day if desired.
Although any form of aerobic exercise is good, high intensity exercise is preferable to low intensity exercise for weight control. It is true the body burns a higher percentage of fat at low to moderate intensities, but the body utilizes a higher *absolute* amount of fat and a higher *absolute* amount of calories at higher intensities. The first part of "workout" is work!

2. Strength Training can also be an effective way to alter body composition, in this case, however, the changes are
somewhat more passive. After the first 6-8 weeks of weight training, the body responds to this exercise stimulus by
increasing the cross sectional diameter of muscle fibers. The total number of calories actively used during weight training is not large; it's about equal to brisk walking. However, this augmented lean body mass raises the resting metabolic rate, thus the total number of calories needed to maintain this increased muscle tissue.
The addition of five pounds of muscle elevates basal caloric requirements by 200 calories/day. One pound of body fat contains 3500 calories. An additional five pounds of muscle would consume at rest the caloric equivalent of one pound of fat every 2-1/2 weeks! This enhanced maintenance requirement continues even during sleep. This is another way to produce a calorie deficit. By increasing one's resting metabolism, the body needs more calories 24 hours/day, 7 days/week even at rest. Again, the body has to make up this difference by drawing upon body fat stores, thus reducing % body fat.
If one combines these types of exercise, you've created a calorie deficit in two different ways. By creating a calorie deficit via exercise rather than diet alone. one does not have to reduce total calorie intake by as much to reduce % body fat, and what body fat is lost is more likely to stay off than with a weight reduction program consisting entirely of caloric restriction. So, if you want to lose excess body fat, the best way is to burn it! If you want to know more about using exercise as a weight control tool, you can contact the Health & Fitness Lab at 745-6531.